Sound barriers are becoming increasingly important for assuring homeowners and potential homeowners and residents proximate major roadways of the ability to peaceful enjoyment of an urban lifestyle. In densely populated suburbia, new residences are now being built in areas that were once deemed undesirable such, for example, as those immediately adjacent to high-speed expressways. Purchasers of these new residences soon become intolerant of the constant bombardment of noise from highway vehicles and travellers and often barrage local authorities with requests to erect expensive sound barriers.
In another instance, construction must at times be carried out in heavily populated areas. Typically, such construction sites are merely surrounded by a wooden or chain link fence formed of a single layer of thin plywood or of metal wire. Construction noise is rarely attenuated by such fences since their primary purpose is to keep trespassers from wandering onto the construction site, rather than preventing machinery noise from projecting outward therebeyond.
In yet another common situation, sound barriers may be employed around sections of airports where intense aircraft engine noise is desirably attenuated. The impact-absorption qualities of such sound barriers are also an important consideration because of the possibility of an out-of-control aircraft careening into the barriers.
To attain their sound absorption qualities, sound barriers often make use of the damping characteristics of certain constituent materials and/or the geometric configurations of their surfaces. The constituent materials may include plastic foam, shredded rubber, sponge, fibers, or any aggregation thereof. These materials are typically encapsulated within an outer shell such, for example, as an aluminum extrusion. The surface geometries of the sound barrier may also include numerous holes and/or gaps so that sound can be trapped and/or absorbed within the sound barrier. Such barriers, however, suffer the disadvantages of relatively high cost and susceptibility to degradation over a short period of time in an environment exposed to the elements.
A particularly common form of sound barrier in use today is that constructed of concrete or masonry, a design that is relatively simple as compared to those previously discussed. Such barriers operate primarily by reflecting sound back toward the roadway; sound absorption or damping is minimal with such barriers and, indeed, is not generally their major intended utility.
Unit cost of a sound barrier is of paramount concern since the barriers must typically extend for at least long sections, often of many miles, of high-speed roadways. Barriers of complex or extravagant structure or requiring highly labor-intensive installation are accordingly generally considered commercially impractical.
Various sound barrier structures are disclosed in the U.S. patented art. For example, the Coburn patent (U.S. Pat. No. 4,643,271) discloses a sound barrier wall construction comprising a plurality of wire cages containing a mixture of crushed stones and shredded tires. Coburn teaches that the crushed stones serve as ballast while the shredded tires provide both sound and shock absorbing qualities.
The Schmanski patent (U.S. Pat. No. 5,272,284) similarly discloses a sound barrier wall comprising a plurality of containment panels or members, each of which is filled with a resilient composite made up of shredded tires (i.e. "rubber chips") and binder materials such as thermosetting resins.
These prior art structures, however, require a great deal of labor, and corresponding expense, to acquire and prepare the materials from which the barrier is constructed and to form the barrier from such materials.